2005 Vol. 25, No. 1
2005, 25(1): 1-5.
Abstract:
In quasi-linear approximation,the electron "transit-time acceleration" by compressional ULF turbulence near the geosynchronous orbit is studied.The frequency range of compressional ULF turbulence is from 2 mHz to 15 mHz.When compressional ULF waves resonate with the background electrons(E<30 keV) and substorm injection electrons(30-300 keV),the electrons with higher-energy increase while the lower-energy electrons decrease,which showed that resonant electrons are accelerated effectively by compressional ULF turbulence.The efficiency of the electron acceleration depends on the character of ULF waves,the larger the amplitude of ULF waves are,the higher the acceleration efficiency is,and the bigger the spectral index is,the lower the acceleration efficiency is.In addition,the more substorm injection electrons are,the more relativistic electrons produced by ‘Transit-time acceleration’ are.Since substorms can offer substorm injection electrons,therefore large flux enhancement events of relativistic electrons(E ≥ 1 MeV) always occur during substorm time.For magnetic storms that are composed of a series of substorms,extremely large flux enhancement events of relativistic electrons can thus occur.
In quasi-linear approximation,the electron "transit-time acceleration" by compressional ULF turbulence near the geosynchronous orbit is studied.The frequency range of compressional ULF turbulence is from 2 mHz to 15 mHz.When compressional ULF waves resonate with the background electrons(E<30 keV) and substorm injection electrons(30-300 keV),the electrons with higher-energy increase while the lower-energy electrons decrease,which showed that resonant electrons are accelerated effectively by compressional ULF turbulence.The efficiency of the electron acceleration depends on the character of ULF waves,the larger the amplitude of ULF waves are,the higher the acceleration efficiency is,and the bigger the spectral index is,the lower the acceleration efficiency is.In addition,the more substorm injection electrons are,the more relativistic electrons produced by ‘Transit-time acceleration’ are.Since substorms can offer substorm injection electrons,therefore large flux enhancement events of relativistic electrons(E ≥ 1 MeV) always occur during substorm time.For magnetic storms that are composed of a series of substorms,extremely large flux enhancement events of relativistic electrons can thus occur.
2005, 25(1): 6-16.
Abstract:
In this paper,the SITEC phenomena is investigated which were caused by the X-class X-ray solar flares occurred from 1996 to 2003.The TEC data which obtained from a global GPS network are used to calculate the TEC increment,ΔTECf,and the variation rate increment,Δ(dTECf/dt),caused by solar flares.It is found that both ΔTECf and Δ(dTECf/dt) are closely related with the flare's maximal X-ray flux and its location on the solar disc.After eliminating the effect of the maximal X-ray fluxes and the locations on solar disc of different flares,results showed that there is a negative relationship between ΔTECf and the distance between the Earth and the Sun.The larger the distance,the smaller is the ΔTECf.Another finding is that Δ(dTECf/dt) correlates with the duration of the flare.Some characteristics of the flares which cause no obvious SITEC are also found.
In this paper,the SITEC phenomena is investigated which were caused by the X-class X-ray solar flares occurred from 1996 to 2003.The TEC data which obtained from a global GPS network are used to calculate the TEC increment,ΔTECf,and the variation rate increment,Δ(dTECf/dt),caused by solar flares.It is found that both ΔTECf and Δ(dTECf/dt) are closely related with the flare's maximal X-ray flux and its location on the solar disc.After eliminating the effect of the maximal X-ray fluxes and the locations on solar disc of different flares,results showed that there is a negative relationship between ΔTECf and the distance between the Earth and the Sun.The larger the distance,the smaller is the ΔTECf.Another finding is that Δ(dTECf/dt) correlates with the duration of the flare.Some characteristics of the flares which cause no obvious SITEC are also found.
2005, 25(1): 17-22.
Abstract:
Three-wave coupling process in parametric excitation is further studied under an isotropic,homogenous and collisional ionospheric background.A general dispersive equation is firstly derived to describe the excitation of waves for a collisional ionosphere.Then,to start with this dispersive equation as well as the two kinds of wave frequencies and vectors matching conditions obtained in the paper [1],the threshold fields of pump waves to trigger overdense and underdense parametric instabilities and the growing rates of the excited plasma waves are obtained and compared with each other.The results show that in the case of overdense heating the threshold value is proportional to both ion and electron collisional frequency,which is much different from the previous results that the threshold only holds a proportional relation with electron collisional frequency.It is also concluded that more powerful HF waves are required to give rise to parametric instability for underdense heating than overdense heating.
Three-wave coupling process in parametric excitation is further studied under an isotropic,homogenous and collisional ionospheric background.A general dispersive equation is firstly derived to describe the excitation of waves for a collisional ionosphere.Then,to start with this dispersive equation as well as the two kinds of wave frequencies and vectors matching conditions obtained in the paper [1],the threshold fields of pump waves to trigger overdense and underdense parametric instabilities and the growing rates of the excited plasma waves are obtained and compared with each other.The results show that in the case of overdense heating the threshold value is proportional to both ion and electron collisional frequency,which is much different from the previous results that the threshold only holds a proportional relation with electron collisional frequency.It is also concluded that more powerful HF waves are required to give rise to parametric instability for underdense heating than overdense heating.
SHANG Sheping,
SHI Jiankui,
GUO Jianshan,
LUO Xigui,
P. M. Kintner,
ZHEN Weimin,
WU Shunzhi,
ZHANG Manlian,
WANG Xiao
2005, 25(1): 23-28.
Abstract:
To investigate the equatorial ionospheric scintillation morphology and the relevant physical processes,one GPS ionospheric scintillation monitor was installed at CSSAR Hainan station.The monitor is built on Plessey GPS Builder-2 development system with its software modified to log signal strength from up to 11 channels at a high data rate(50 samples/s).It is suits the high time resolution studies of scintillation spectral and temporal characteristics and also can be used to perform the statistic analysis of scintillation signals.The preliminary analysis results of L-band ionospheric scintillations during Jul.-Dec.2003 show that ionospheric scintillations mainly occur near from sunset to midnight,where the onset and end time are evidently more advanced in Nov.-Dec.than in Jul.-Aug.;the occurrence rate and intensity of ionospheric scintillations are evidently more enhanced in Sept.-Nov.than in other months,and reach their peaks in Oct.;there is the strong randomness for the day-to-day variability of ionospheric scintillations,and the scintillation occurrence reaches their peak during the magnetic quiet days from the end of Sept.to the middle of Oct.near autumnal equinox;the increase of solar and geomagnetic activities generally may limit the occurrence of ionospheric scintillations,especially near autumnal equinox.
To investigate the equatorial ionospheric scintillation morphology and the relevant physical processes,one GPS ionospheric scintillation monitor was installed at CSSAR Hainan station.The monitor is built on Plessey GPS Builder-2 development system with its software modified to log signal strength from up to 11 channels at a high data rate(50 samples/s).It is suits the high time resolution studies of scintillation spectral and temporal characteristics and also can be used to perform the statistic analysis of scintillation signals.The preliminary analysis results of L-band ionospheric scintillations during Jul.-Dec.2003 show that ionospheric scintillations mainly occur near from sunset to midnight,where the onset and end time are evidently more advanced in Nov.-Dec.than in Jul.-Aug.;the occurrence rate and intensity of ionospheric scintillations are evidently more enhanced in Sept.-Nov.than in other months,and reach their peaks in Oct.;there is the strong randomness for the day-to-day variability of ionospheric scintillations,and the scintillation occurrence reaches their peak during the magnetic quiet days from the end of Sept.to the middle of Oct.near autumnal equinox;the increase of solar and geomagnetic activities generally may limit the occurrence of ionospheric scintillations,especially near autumnal equinox.
2005, 25(1): 29-36.
Abstract:
By using the Alternative-Direction-Implicit(ADI) scheme,a fully nonlinear,compressible and two-dimensional model is developed to numerically study the nonlinear propagations of gravity-wave-packets with different initial amplitude.The simulations show that the nonlinear effects depend strongly on the wave amplitude.The nonlinearity will damp the wave amplitude growth significantly,change the vertical wave numbers,and alter obviously the vertical velocity of energy transmission.The mean flows are accelerated extensively and greatly in the nonlinear propagation of a gravity wave packet with large amplitude.
By using the Alternative-Direction-Implicit(ADI) scheme,a fully nonlinear,compressible and two-dimensional model is developed to numerically study the nonlinear propagations of gravity-wave-packets with different initial amplitude.The simulations show that the nonlinear effects depend strongly on the wave amplitude.The nonlinearity will damp the wave amplitude growth significantly,change the vertical wave numbers,and alter obviously the vertical velocity of energy transmission.The mean flows are accelerated extensively and greatly in the nonlinear propagation of a gravity wave packet with large amplitude.
2005, 25(1): 37-43.
Abstract:
Aiming at numerically studying the global nonlinear propagation of atmospheric tides,a new fully nonlinear numerical model in a three dimensional spherical coordinates is established.In the construction of the numerical model,the spectral allocation method was used to numerically resolve the Navier-Stokes equations,which was taking as the governing equations.In the specification of the boundary conditions,periodic and projected characteristic line boundaries are chosen as the zonal and vertical boundaries,respectively;moreover,the polar boundary are also carefully specified.For the purpose of examining our newly established model,the global nonlinear propagation of a gravity-wave packet with large scales is simulated and compared with a previou simulation.The calculation result exhibits the essential characteristics of the nonlinear propagation of a gravity-wave packet in atmosphere:the whole wave packet propagates upward and the wave-associated disturbance velocity increases with the increasing height,which is quantitatively consistent with the previous simulation.These suggested that our numerical model and the nonlinear simulation are reliable.
Aiming at numerically studying the global nonlinear propagation of atmospheric tides,a new fully nonlinear numerical model in a three dimensional spherical coordinates is established.In the construction of the numerical model,the spectral allocation method was used to numerically resolve the Navier-Stokes equations,which was taking as the governing equations.In the specification of the boundary conditions,periodic and projected characteristic line boundaries are chosen as the zonal and vertical boundaries,respectively;moreover,the polar boundary are also carefully specified.For the purpose of examining our newly established model,the global nonlinear propagation of a gravity-wave packet with large scales is simulated and compared with a previou simulation.The calculation result exhibits the essential characteristics of the nonlinear propagation of a gravity-wave packet in atmosphere:the whole wave packet propagates upward and the wave-associated disturbance velocity increases with the increasing height,which is quantitatively consistent with the previous simulation.These suggested that our numerical model and the nonlinear simulation are reliable.
2005, 25(1): 44-51.
Abstract:
Data observed by the Wuhan meteor radar(20 February 2002-10 November 2003) have been used to study the quasi 16-day oscillations in the mesosphere and lower thermosphere(MLT),which is a type of planetary wave with period ranges from 12 to 20 days.The results show that the zonal components are generally stronger than the meridional components.(1) In the year of 2002 and 2003,the largest amplitudes appear in early autumn(10 September-10 October) when the zonal background winds are eastward.The largest amplitude value derived from the Lomb-Scargle(L-S) periodograms is about 16 m/s.A second maximum appears in the summer of 2002,but not in the summer of 2003.There are no strong wave activities in the winter months of both years.(2) In 2002,the 16 day waves are strong from 86 to 98km with the maximum at about 90km to 94km,but they are strong at lower altitudes in 2003.The energy of the 16-day wave propagates upward in autumn,which means the wave originate from lower atmosphere,but the direction of wave energy propagation is downward in summer of 2002,which means the 16-day waves may propagate from the southern hemisphere.
Data observed by the Wuhan meteor radar(20 February 2002-10 November 2003) have been used to study the quasi 16-day oscillations in the mesosphere and lower thermosphere(MLT),which is a type of planetary wave with period ranges from 12 to 20 days.The results show that the zonal components are generally stronger than the meridional components.(1) In the year of 2002 and 2003,the largest amplitudes appear in early autumn(10 September-10 October) when the zonal background winds are eastward.The largest amplitude value derived from the Lomb-Scargle(L-S) periodograms is about 16 m/s.A second maximum appears in the summer of 2002,but not in the summer of 2003.There are no strong wave activities in the winter months of both years.(2) In 2002,the 16 day waves are strong from 86 to 98km with the maximum at about 90km to 94km,but they are strong at lower altitudes in 2003.The energy of the 16-day wave propagates upward in autumn,which means the wave originate from lower atmosphere,but the direction of wave energy propagation is downward in summer of 2002,which means the 16-day waves may propagate from the southern hemisphere.
2005, 25(1): 52-56.
Abstract:
When satellite moves around the earth or moon,its position and moving behavior should be held in order to track and control it.Due to the self rotation and revolution of the earth,the description of relative motion between earth and satellite become complicated.And the time delay and Doppler shift of an aimed satellite that relative to any two observation sites change at all times.VLBI correlation processor is a key technical instrument in space probing and satellite observation.The principle of correlation model of FX and XF is used to deal with observational data.Time delay and fringe stopping of VLBI correlation model is modified based on FX model,and a mirror "1/n Multiplier" model of time delay and fringe stopping is brought foward.Through analysis of the actual observational data and the changing trend of residual time delay and variance distribution,a better model of time delay compensation and fringe stopping is shown.
When satellite moves around the earth or moon,its position and moving behavior should be held in order to track and control it.Due to the self rotation and revolution of the earth,the description of relative motion between earth and satellite become complicated.And the time delay and Doppler shift of an aimed satellite that relative to any two observation sites change at all times.VLBI correlation processor is a key technical instrument in space probing and satellite observation.The principle of correlation model of FX and XF is used to deal with observational data.Time delay and fringe stopping of VLBI correlation model is modified based on FX model,and a mirror "1/n Multiplier" model of time delay and fringe stopping is brought foward.Through analysis of the actual observational data and the changing trend of residual time delay and variance distribution,a better model of time delay compensation and fringe stopping is shown.
2005, 25(1): 57-62.
Abstract:
The Beidou Positioning and Navigation System in the stand-alone mode cannot accomplish real-time 3-D passive positioning due to the limited number of constellation,but when aided by Pseudolites,through which the number and geometry of constellation is improved,it is capable of realizing high-precision passive positioning.Pseudo-satellites,also called pseudolites(PLs),which are the transmitters of navigation satellite-like signals,have the similar principle and function as spaceborne satellites,hence can provide the additional ranging source and thereby improving the geometry and increasing the accuracy,integrity,availability and reliability of the positioning results.And by simple,software only modifications,an existing satellite receiver can acquire PL signals and derive pseudoranges or carrier-phase measurements to be used in a navigation algorithm.As well known,such performances as accuracy of satellite-based positioning system are heavily dependent on the number and geometric distribution of satellites being tracked,and GDOP is a right measure of the geometry of the constellation.Therefore in the paper,the impacts of various locations and geometries of PLs on the accuracy of the augmented system are comprehensively investigated based on GDOP,and the conclusions obtained are the useful references for configuring PLs rationally as to improve further the performances of the system.
The Beidou Positioning and Navigation System in the stand-alone mode cannot accomplish real-time 3-D passive positioning due to the limited number of constellation,but when aided by Pseudolites,through which the number and geometry of constellation is improved,it is capable of realizing high-precision passive positioning.Pseudo-satellites,also called pseudolites(PLs),which are the transmitters of navigation satellite-like signals,have the similar principle and function as spaceborne satellites,hence can provide the additional ranging source and thereby improving the geometry and increasing the accuracy,integrity,availability and reliability of the positioning results.And by simple,software only modifications,an existing satellite receiver can acquire PL signals and derive pseudoranges or carrier-phase measurements to be used in a navigation algorithm.As well known,such performances as accuracy of satellite-based positioning system are heavily dependent on the number and geometric distribution of satellites being tracked,and GDOP is a right measure of the geometry of the constellation.Therefore in the paper,the impacts of various locations and geometries of PLs on the accuracy of the augmented system are comprehensively investigated based on GDOP,and the conclusions obtained are the useful references for configuring PLs rationally as to improve further the performances of the system.
2005, 25(1): 63-69.
Abstract:
The simulation of GPS observation on a moving low-earth-orbiter(LEO) is to simulate the measured signals that would be received by a GPS receiver on a LEO.Since a LEO and GPS satellites are in a three-dimensional coordinate system,the values of various errors and observation noise level can be well calculated and known in advance,so using GPS simulation of the observations of a onboard GPS receiver can be of great help for judging some important parameters in orbit determination such as ambiguity resolution method,Kalman filtering technique and so on.In this paper,the method of simulating GPS observations of an onboard GPS receiver is systematically studied.The emphasis is first put on principle and mathematical model.Then,the GPS dual-frequency P codes and carrier-phase observations of potential onboard GPS receivers are simulated by employing some elaborately selected error modes.The results show that the simulated observations of CHAMP satellite obtained from software developed by the author are very close to the real measurements in-situ and such is observation noise level,therefore the simulation method used in this paper can meet the needs of different users of GPS data.
The simulation of GPS observation on a moving low-earth-orbiter(LEO) is to simulate the measured signals that would be received by a GPS receiver on a LEO.Since a LEO and GPS satellites are in a three-dimensional coordinate system,the values of various errors and observation noise level can be well calculated and known in advance,so using GPS simulation of the observations of a onboard GPS receiver can be of great help for judging some important parameters in orbit determination such as ambiguity resolution method,Kalman filtering technique and so on.In this paper,the method of simulating GPS observations of an onboard GPS receiver is systematically studied.The emphasis is first put on principle and mathematical model.Then,the GPS dual-frequency P codes and carrier-phase observations of potential onboard GPS receivers are simulated by employing some elaborately selected error modes.The results show that the simulated observations of CHAMP satellite obtained from software developed by the author are very close to the real measurements in-situ and such is observation noise level,therefore the simulation method used in this paper can meet the needs of different users of GPS data.
2005, 25(1): 70-75.
Abstract:
Lunar soil simulants are geochemical copycats of lunar sample.They have similar chemical composition,mineralogy,particle size distribution,and engineering properties with lunar sample.Simulants of lunar rocks and soils have been developed to satisfy the requirements of a variety of scientific and engineering investigations.They are essential to meet the system requirements for lunar exploration and in support of future human activities on the Moon.Such studies include material handling,construction,excavation,and transportation.The simulants is also appropriate for research on dust control,spacesuit durability,and agriculture.
Five lunar soil simulants,JSC-1,MLS-1,MLS-2,MKS-1,FJS-1 are reviewed in the paper.Their starting materials,preparation,and characterization(chemical composition,mineralogy,particle size distribution,specific gravity,angle of internal friction,and cohesion) are also listed.
China will realize the first lunar exploration before 2007.So it is an essential and pressing task to develop lunar soil simulants series corresponding to average chemical and mineral composition of lunar sample at Apollo and Luna landing sites.The tentative ideas of developing new lunar simuants series based on geologic investigations were brought forward in the end.
Lunar soil simulants are geochemical copycats of lunar sample.They have similar chemical composition,mineralogy,particle size distribution,and engineering properties with lunar sample.Simulants of lunar rocks and soils have been developed to satisfy the requirements of a variety of scientific and engineering investigations.They are essential to meet the system requirements for lunar exploration and in support of future human activities on the Moon.Such studies include material handling,construction,excavation,and transportation.The simulants is also appropriate for research on dust control,spacesuit durability,and agriculture.
Five lunar soil simulants,JSC-1,MLS-1,MLS-2,MKS-1,FJS-1 are reviewed in the paper.Their starting materials,preparation,and characterization(chemical composition,mineralogy,particle size distribution,specific gravity,angle of internal friction,and cohesion) are also listed.
China will realize the first lunar exploration before 2007.So it is an essential and pressing task to develop lunar soil simulants series corresponding to average chemical and mineral composition of lunar sample at Apollo and Luna landing sites.The tentative ideas of developing new lunar simuants series based on geologic investigations were brought forward in the end.
2005, 25(1): 76-80.
Abstract:
With the rush development of the microelectronics technology and the increasing boost of the high-performance need in space mission,present space-level radiation-hardened components and technology cannot meet the high-performance need of spacecraft.That makes it possible to use Commercial-Off-The-Shelf(COTS) components with high-performance in space application.The space requirements to COTS products is summarized in this paper.The advantages of using COTS parts are the increased functionality,the speed of the instrument,less power consuming and lower cost compared to the space-level components.However,not all COTS parts are suitable for utilization in space applications.Most of them are designed to operate in the ordinary earth environment and are not intended to withstand the radiation environments of space.The radiation in space can cause permanent damage in some types of electronic components.This paper also points out the problems and risks associated with the use of COTS parts in spacecraft,and presents the current status and perspective of COTS components in space application.
With the rush development of the microelectronics technology and the increasing boost of the high-performance need in space mission,present space-level radiation-hardened components and technology cannot meet the high-performance need of spacecraft.That makes it possible to use Commercial-Off-The-Shelf(COTS) components with high-performance in space application.The space requirements to COTS products is summarized in this paper.The advantages of using COTS parts are the increased functionality,the speed of the instrument,less power consuming and lower cost compared to the space-level components.However,not all COTS parts are suitable for utilization in space applications.Most of them are designed to operate in the ordinary earth environment and are not intended to withstand the radiation environments of space.The radiation in space can cause permanent damage in some types of electronic components.This paper also points out the problems and risks associated with the use of COTS parts in spacecraft,and presents the current status and perspective of COTS components in space application.
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Publisher：Science Press
ISSN：ISSN 0254-6124
CN：CN 11-1783/V
Editor chief：WU Ji
Counselor：Gu YiDong
Deputy-chief-editor：
CAO Jinbin
FALANGA Maurizio (Switzerland)
FU Suiyan KANG Qi
LIN Baojun LIN Yangting
SHI Jiancheng YANG Huigen
YANG Zhen ZHANG Shuangnan
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